AIO to my best friend accusing me of coming onto her man?

Alright, strap on because this is going to be a long stupid one, made even dumber by my tendency to over explain everything.

Quick background: “Emily” and I have been friends for four years. The past year has been pretty rough on me, with a bunch of health and family-related issues, plus the end of my relationship with the person I thought I was going to marry. I truly came to rely on Emily during this time and our friendship blossomed to the point where I would confidently say we’re best friends. Emily has been with her boyfriend “Spencer” for about eight months, and they’ve been living together for two. Since then, he’s been gradually inserting himself into the plans we make with our usual (predominantly female) friend group from before he came along. Meaning, if we have five hangouts in a month, he’s there for 4/5 of them, often without my knowledge until we actually meet up and he’s just… there.

Currently, I’m not drinking due to a treatment that I’m undergoing, so I’m often the designated driver and regularly pick up Emily at her place, then Spencer randomly comes and invites himself into my car. The first few times I protested, they both just looked at me confused, as though we had all agreed from the start that he’d be coming along, and Emily seemed really hurt, and so I let it slide. I simply compromised by making sure my solo hangouts with Emily always started at my place so he couldn’t join. Irritatingly enough, he actually did try to just.. waltz inside my house this one time, and then had to awkwardly pretend he was only dropping Emily off when I called him out. Still, I never thought much of Spencer in general, only saw him as a mildly annoying NPC who happens to be around sometimes whenever I see my friend. Anyhow, we are all mid to late 20s. In other words, TOO DAMN GROWN for this sort of drama.

Back to the main story: This happened over a week ago. I certainly don’t intend to make excuses for anybody, but the three of us went clubbing and Emily and Spencer were pretty drunk at this point. It’s the first time the three of us ended up going out together like this, which really only happened because other people cancelled at the last minute. I thought it’d be ok and I wouldn't feel like a total third wheel, because the owner of this club happens to be our only mutual friend with Spencer and he’s often around to chat.

Anyhow, this went down just as we were calling it a night. The club is on a second floor, and the exit leads to a hallway with some stairs, elevator, and a door to the toilet. As we were exiting the club, I let them know that I’m heading to the restroom and to wait downstairs.

Few minutes later, I finish up and make my way down the stairs to join them at the landing. Spencer just stares at me for a moment, gives this drunk stupid grin and goes, “Wow, you seriously need to ask (bar owner friend) for a job, you look like you’d be a great bouncer if you know what I mean!” then cups his hands to his chest as if he had huge boobs and was bouncing them around. Now, Spencer is cross-eyed, so I gave what I thought was a dismissive scoff, dry laugh, and retorted “Don’t worry guy, nobody can quite tell just what you’re looking at.” He stared blankly for a moment and then laughed it off. The whole time, Emily was just quiet and looking off to the side, pretending that she didn’t hear any of this interaction. I was really annoyed, but since I thought I’d put him in his place, I figured that was that and went to drop them off as usual. Mostly, I didn’t want to embarrass Emily any further.

A few days later, I’d genuinely forgotten about this whole situation. I also figured they’d had too much to drink and didn’t remember that stupid interaction. This weekend, I intended to have a lighthearted but serious one-on-one with Emily and tell her she needs to set firm boundaries with Spencer, without making this issue bigger than it needs to be. But when I texted her last night to confirm, she immediately started being super passive-aggressive and insulting me, saying I need to apologize to her and Spencer for coming onto him.. I’ve NEVER seen this type of behavior from her.

I have no idea how any of this could’ve been misinterpreted so disastrously. I hate confrontation in general. She hasn’t responded and I’ve been anxious all day, thinking holy shit. I’m about to lose my best friend in the dumbest fucking way. AIO?